Email has provided a wide range of increased functionality to users of computing devices, such as desktop computers, wireless phones, and so on. Email employs standards and conventions for addressing and routing such that the email may be quickly and efficiently delivered across a network (e.g., the Internet, a corporate intranet, and so on) utilizing a plurality of devices. In this way, a sender of the email incurs minimal costs to transmit the email to an intended recipient, even if the email is transmitted across the world. Because of this minimal cost and speed of delivery, the prevalence of email has continued to expand such that email is now considered an indispensable part of everyday life.
Unfortunately, as the prevalence of email has continued to expand, the amount of “spam” encountered by the user has also continued to increase. Spam is typically thought of as an email that is sent to a large number of recipients, such as to promote a product or service. As previously stated, because transmitting an email generally costs little or nothing to the sender, “spammers” have developed which send the equivalent of junk mail to as many users as can be located. Even though a minute fraction of the recipients may actually desire the described product or service, this minute fraction may be enough to offset the minimal costs in sending the spam. Consequently, a vast number of spammers are responsible for communicating a vast number of unwanted and irrelevant emails. Thus, a typical user may receive a large number of these irrelevant emails, thereby hindering the user's interaction with relevant emails. In some instances, for example, the user may be required to spend a significant amount of time interacting with each of the unwanted emails in order to determine which, if any, of the emails received by the user might actually be of interest.
To protect against spam, spam filters may be employed which filter the email based on a variety of considerations, such as sender address and number of emails sent from that sender address. One effective method is to observe the behavior of a sender over time; a sender that is responsible for a large number of spam messages accumulates a bad reputation and further mail from them can be filtered more aggressively. However, email forwarders (e.g. school alumni addresses) indiscriminately forward mail—both good and spam, and may erroneously accumulate a reputation of a spammer. Therefore, the spam filter may further complicate the user's interaction with the forwarded emails, such as removing the emails altogether, routing the forwarded emails to a spam folder, and so on.
Therefore, there is a continuing need for techniques that may be employed to identify email forwarders.